TERSE

TERSE: a transmission and emission reconstruction environment for SPECT,
has been developed at the University of Michigan
by Jeff Fessler and Edward Ficaro,
in a collaboration between
the Department of Electrical Engineering and Computer Science (EECS)
and the Division of Nuclear Medicine.

TERSE has been adopted for routine use in cardiac scans
at the University of Michigan Medical Center,
and its first years of use
over 2000 cardiac scans were reconstructed using this method.
We initially used a Picker PRISM 3000 triple-head SPECT system
for cardiac scans,
with an Americium transmission source
developed at UM
opposing a 65-cm fan-beam collimator,
with parallel-beam collimators on the other two heads.
All three heads collection emission data.
An iterative coordinate ascent algorithm in the TERSE package
produces cross-sectional thorax attenuation images
from the fan-beam transmission data
in which the lungs, spine, and soft-tissue are clearly seen.
The ring artifact that is intrinsic to conventional FBP images
from truncated measurements
is eliminated by our statistical approach.
We incorporate these nonuniform attenuation characteristics
into an emission reconstruction algorithm,
which yields images with improved uniformity
of the cardiac wall in normal patients, thus reducing the false positives
(which lead to unnecessary risky and expensive catheterization procedures).

Unlike commercially available iterative reconstruction methods,
TERSE is based on regularized statistical methods,
and uses algorithms with guaranteed global convergence.
This means the image properties,
such as noise and spatial resolution,
are more predictable and controllable
than with the popular unregularized methods.
The algorithms converge quickly to a stable image.
The trade-off between resolution and noise is controlled directly by the user,
not indirectly by the number of iterations, number of counts, etc.

TERSE has been evaluated by ROC studies using both human observers
and semi-automatic polar-map based observers,
and statistically significant improvements in diagnostic accuracy
have been demonstrated
over conventional FBP without attenuation correction.
See 1996 Circulation paper:
"Simultaneous transmission/emission myocardial perfusion tomography: Diagnostic accuracy of attenuation-corrected 99m-Tc-Sestamibi SPECT"
by Ficaro et al.
A full reference to the paper
is available in the publication list at
http://web.eecs.umich.edu/~fessler/papers.)